Vortex shedding flowmeters are well known in the art. Such flowmeters measure the volumetric rate of flow of a fluid in a conduit through the generation of hydrodynamic oscillations at a rate which is proportional to the flow rate. The oscillations are generated by placing a blunt obstruction or bluff in the fluid conduit, which causes vortices to be shed off the bluff body into the fluid.
There are several known means for sensing these vortices, including ultrasonic detectors, silicon strain gauges, piezoelectric devices, and self-heated thermocouples, which detect lift forces acting on the bluff body, or the flow currents caused by the vortex generation. These known techniques have several disadvantages, including limited sensitivity to flow, high sensitivity to vibration and flow-induced noise, limited temperature range, and possible difficulty associated with the use of electrical signals in potentially hazardous environments.